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SilverSolder:
--- Quote from: nctnico on March 04, 2021, 03:32:30 pm ---Now try to figure out how HP never came up with the idea of having a fuse in series with the output of a PSU ^-^
--- End quote ---
I guess you'd have to sense the voltage on both sides of the fuse to do a really good job... it starts to get expensive! :D
HighVoltage:
The problem I have with crowbar is that I did not know about it, until I read the manual. :-DD
The brand new Agilent PSU that I killed a few years back, was a E3648A series PSU.
The heavy crowbar traces were burned away completely.
Luckily the traces could be repaired with heavy copper wires.
Now I am aware !
bdunham7:
--- Quote from: nctnico on March 04, 2021, 03:32:30 pm ---Now try to figure out how HP never came up with the idea of having a fuse in series with the output of a PSU ^-^
--- End quote ---
You tell me. Some other manufacturers have them, some don't. I've worked on quite a few bench PSUs in recent years and although later model HPAK PSUs like the E36xx series are expensive and widely held in high regard, they don't impress me all that much. There's no reason to let them go up in flames rather than simply have a large fuse to protect against gross overloads. Or simply use an OVP system other than a crowbar.
Berni:
I think a fuse would be a good idea to have on a PSU with such a SCR crowbar circuit.
Its not even that difficult to get around the fuse voltage drop. All you do is hook up the sense wire after the fuse. Since the voltage sense is a high impedance input it is a lot easier to protect it using the good ol resistor and TVS diode.
Tho that fuse then only protects the PSU from the DUT. If the crowbar trips because of a fault inside the PSU it wont blow, but then again at that point you need an extensive PSU repair anyway, and a common fault with linear PSUs that makes them output too much voltage is a blown pass transistor, so your power stage is already dead anyway, eventually a fuse at the transformer would blow to stop it from catching fire.
tautech:
Why is it that foldback current limiting isn't incorporated in a 'quality' PSU FFS, even a $30 SMPS has such a feature as it's hardly a new leading edge technology when it's been around for decades.
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